I. Field of The Invention
The present invention relates generally to agricultural balers and, in particular, to density control methods and apparatus for such balers.
II. Prior Art and Other Considerations
Agricultural balers have a bale case into which crop or silage material is introduced. The bale case, generally of a rectangular shape, is defined by rails which determine the height and width of the bale case. A plunger is reciprocably disposed in a forward portion of the bale case to form crop material into rectangular bales. These rectangular bales are pushed through a rearward portion of the bale case where they are bound in a conventional manner with suitable material such as twine before being discharged from the baler.
In the baler art it is known that bale density may be controlled by changing the position of one or more of the rails defining the bale case. Numerous types of mechanisms have been provided for performing this function such as those shown in U.S. Pat. Nos. 4,125,071; 4,037,528; and 4,489,648. In various ones of these known mechanisms tensioning systems comprising hydraulic cylinders are actuated to change the position of the bale case rails.
Various prior art methods exist for controlling the actuation of the hydraulic cylinders and for thereby changing the position of the bale case rails in order to control the density of the material being baled therein. U.S. patent application Ser. No. 773,471, entitled "Bale Density Control Sensing Apparatus and Method" simultaneously filed herewith by Cecil R. Sudbrack et al. and incorporated herein by reference, discloses new method and apparatus wherein sensor means are provided for monitoring the compression load on each of two connecting rods which connect a plunger element to plunger driving means. Sensors such as strain gauge sensors are used for electronic decisions regarding adjustments of the hydraulic cylinders necessary for controlling bale density. The electronic decisions are based on the compression load required to push the material being baled through the tensioned bale case. The required compression load is dependent upon factors such as the degree of frictional drag between the bale case and the material being baled. By using the sensors to monitor the compression load and by actuating the hydraulic cylinders comprising the bale case tensioning system to maintain a constant compression load, a constant bale density results with respect to each charge of material introduced into the bale case.
The amount of crop material being introduced into a bale case can fluctuate greatly as the tractor-pulled baler travels over a windrowed field. Fluctuations in crop flow into the bale case can present problems when the compression load is being continually monitored for the purpose of adjusting the bale case tensioning system. For example, when a baler enters the headlands, crop material ceases to enter the bale case. When the baler is in the headlands the compression load on the connecting rods significantly decreases. If the tension rail pressure were to be increased to tighten the bale case in accordance with the decreased compression load, the baler would enter the next windrow with a highly tensioned rail pressure. Ingestion of a considerable amount of new crop material into a highly tensioned bale case can overload the connecting rods which are used to drive the plunger.
In view of the foregoing, it is an object of the present invention to provide bale density control method and apparatus which takes into consideration fluctuations in the amount of crop flow into the bale case.
An advantage of the present invention is the provision of method and apparatus wherein crop ingestion measurements are made by the same sensors used for bale density control.
Another advantge of the present invention is the provision of method and apparatus wherein crop ingestion measurements take into consideration power take off (PTO) speed.
Yet another advantage of the present invention is the provision of method and apparatus wherein PTO speed is determined from information available from bale density control sensors, thus avoiding the employment of a separate PTO sensor and the external wiring associated therewith.